title: Effects of feeding polyclonal antibody preparations on rumen fermentation patterns, performance, and carcass characteristics of feedlot steers.
abstract: In a previous study, preparations of polyclonal antibodies (PAP) against Fusobacterium necrophorum (PAP-Fn) or Streptococcus bovis (PAP-Sb) were successful in decreasing ruminal counts of target bacteria and increasing ruminal pH in steers fed high-grain diets. The objective of this study was to evaluate the effects of feeding PAP-Fn or PAP-Sb on performance, carcass characteristics, and ruminal fermentation variables of feedlot steers. In Exp. 1, during 2 consecutive years, 226 or 192 Angus and Angus crossbred steers were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. When measured on a BW basis, steers fed only PAP-Sb had a greater G:F (P < 0.05) than those fed no PAP. Nevertheless, when both PAP were fed, feed efficiency was similar (P > 0.10) to steers fed no PAP or only PAP-Sb. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased (P < 0.05) dressing percentage. Steers receiving PAP-Fn (alone or in combination with PAP-Sb) had a decreased severity of liver abscess (P < 0.05). No differences (P > 0.10) were observed in any other carcass characteristics. In Exp. 2, sixteen ruminally cannulated Angus crossbred steers (BW = 665 +/- 86 kg) were fed a high-grain diet containing either PAP-Sb or PAP-Fn, or both. Feeding only PAP-Fn or PAP-Sb for 19 d decreased (P < 0.05) ruminal counts of S. bovis when compared with steers fed both or no PAP. The ruminal counts of F. necrophorum in steers fed PAP-Fn alone or in combination with PAP-Sb were decreased by 98% (P < 0.05) after 19 d, when compared with the counts in control steers. Mean daily ruminal pH was greater (P < 0.05) in steers fed both PAP when compared with feeding either or no PAP. Ruminal pH in the first 4 h after feeding was greater (P < 0.05) for steers receiving PAP-Fn alone or in combination with PAP-Sb. Steers receiving either PAP alone or in combination had less (P < 0.05) ruminal NH(3)-N concentrations in the first 4 h after feeding when compared with those of control steers. Polyclonal antibody preparations against S. bovis were effective in enhancing G:F of steers fed high-grain diets, but dressing percentage was decreased. Mechanisms of enhancement of G:F remain unknown but may be related to changes in ruminal counts of target bacteria and associated effects on ruminal fermentation products.
authors.affiliation: Department of Animal Science, University of Minnesota, St. Paul 55108, USA.
authors.forename: N
authors.initials: N
authors.lastname: DiLorenzo
authors.forename: C R
authors.initials: CR
authors.lastname: Dahlen
authors.forename: F
authors.initials: F
authors.lastname: Diez-Gonzalez
authors.forename: G C
authors.initials: GC
authors.lastname: Lamb
authors.forename: J E
authors.initials: JE
authors.lastname: Larson
authors.forename: A
authors.initials: A
authors.lastname: DiCostanzo
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000008:administration & dosage / Q000494:pharmacology*; D001823:Body Composition / Q000187:drug effects*; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism* / Q000382:microbiology; D004032:Diet / Q000662:veterinary; D005285:Fermentation / Q000187:drug effects*; D005675:Fusobacterium necrophorum / Q000276:immunology; D008297:Male; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology; D016985:Streptococcus bovis / Q000276:immunology; D013997:Time Factors; D015430:Weight Gain / Q000187:drug effects*
chemical_list: D000907:Antibodies, Bacterial